This Program Project Grant (PPG) began 35 years ago when we delineated the LDL receptor pathway for control of cholesterol metabolism and showed that defects in the LDL receptor produce Familial Hypercholesterolemia and atherosclerosis. After 35 years, our goals have broadened and the participants have increased, but the focus remains the same: to understand the genetic and molecular basis for regulation of lipid and lipoprotein metabolism and to use this knowledge to prevent and treat lipid-related diseases i.e., atherosclerosis and Metabolic Syndrome. During the last 5 years, we published 164 papers, reporting the following major advances: 1) discovery of Scap as the sensing receptor for membrane cholesterol that controls SREBP processing, thereby determining LDL receptor number and plasma LDL level; 2) discovery of mutations in PCSK9 that lower plasma LDL and decrease heart attacks as much as 88%; 3) demonstration that PCSK9 functions extracellularly to bind and degrade LDL receptors, an observation that stimulated pharmaceutical companies to develop antibodies that block PCSK9 and lower LDL; 4) elucidation of the hydrophobic handoff mechanism for export of LDL-derived cholesterol from lysosomes; 5) delineation of the sterol-regulated, ubiquitin-mediated pathway for degradation of HMG CoA reductase and lnsig-1; 6) discovery of GOAT, the enzyme that attaches octanoic acid to ghrelin, a covalent modification required for ghrelin's activity in controlling appetite and blod sugar; 7) identification of a protein, MIG12, that activates fatty acid synthesis in liver; 8) discovery of 25-hydroxycholesterol as an immunoregulatory sterol that links the innate and adaptive immune systems; and 9) elucidation of an LRP1- mediated signaling pathway that protects vascular smooth muscle cells against atherosclerosis. We now apply for a 5-year renewal (Years 36-40) to further study these and related phenomena through an integrated, multidisciplinary approach. We propose to learn more about known molecules and to discover new ones that regulate lipid and lipoprotein metabolism as it relates to disease. We will continue to study these processes at all levels - molecules (i.e., gene, mRNA, protein), cells, experimental animals, and human patients. We will employ multiple approaches - biochemistry, molecular biology, genetics, cell biology, gene-manipulated mice, animal physiology, clinical genetics, and genomics. Such an integrated interdisciplinary approach is possible only through continued support of this PPG.